How to make sure SSPI crypt/sign functions does not change the input data buffer?

HI All

I'm playing with EncryptMessage/DecryptMessage/MakeSignature/
VerifySignature functions on SSPI/Kerberos. There seems quite a lot of
combination to arrange the SecBufferDest argument. Is there a way to
make sure that the input data (includes data and signature) are never
changed in-place?